Valve control system

ABSTRACT

Apparatus is provided for actuating an intermittent motion control element, such as a rotary valve. A pulse generator establishes periodic actuating pulses at a frequency corresponding to the amplitude of a control signal. Rotation of a motor is regulated by these pulses through control circuits which can include a time delay relay to hold the motor stationary for a given time at a selected point in the cycle.

United States Patent Morgan [4 Apr. 25, 1972 54] VALVE CONTROL SYSTEM3,467,905 9/1969 Thornhill et a]. ..3l8/443 [72] Inventor: John A.Morgan, Bartlesvllle, Okla. Primary Examiner aemard A. Gilheany [73]Assignee: Phillips Petroleum Company Assistant Examiner-W. E. Duncanson,Jr. [22} Filed: July 24, 1970 Attorney-Young and Quigg [21] Appl. No.:57,990 57 B TR CT Apparatus is provided for actuating an intermittentmotion [52] "318/443 control element, such as a rotary valve A pulsegenerator [51] "H02? 5/10 establishes periodic actuating pulses at afrequency cor- [58] Field of Search ..3 1 8/443, 444, 466 responding tothe amplitude of a comm] signaL Rotation of a motor is regulated bythese pulses through control circuits [56] References Cited which caninclude a time delay relay to hold the motor sta- UNn-ED STATES PATENTStionary for a given time at a selected point in the cycle. 3,257,5986/1966 Settles 1 8/443 6 Claims, 2 Drawing Figures 24 3= PULSE/ 25 2a 29(o GENERATOR :U i r 2 3| as 2 I [33 l i 37 I Patented April 25, 1972CATALYST COMPUTER SOLVENT PRODUCT MONOMER COOLANT 5 a WT 4 II 4 3 L M M5 4 3 a 0 llrw \f \l, K a a 5 R 4 m fl M fiE m We T 3 INVENTOR. J. A.MORGAN FIG. 2

ATTORNEYS VALVE CONTROL SYSTEM In various types of chemical operationsit is desirable to introduce materials in discrete masses rather thancontinuously. One such example occurs in polymerization reactions.utilizing solid catalysts which are introduced into a reactor in theform of a slurry. It is difficult to introduce such a materialcontinuously at relatively low flow rates because the solid particlesmay bridge and plug the control valve. In order to overcome thisproblem, rotary valves have been developed, such as described in U.S.Pat. No. 3,l67,398. These valves employ a rotary plug which has achamber therein to receive a predetermined quantity of material to bemetered. In one position the chamber is filled with the material, and inanother position the material is forced through the valve. When such avalve is employed in an automatic control system, a need exists forapparatus to move the valve intermittently between such positions at arate which is proportional to'the amplitude of a control signal. Oneexample of apparatus which can be employed for this purpose is describedin U.S. Pat. No. 3,467,905.

In accordance with the present invention, improved apparatus is providedwhich is capable of intermittently operating equipment such as a rotaryvalve. This apparatus utilizes relays, including a time delay relay, tocontrol the application of current to a motor which is employed torotate the valve. A selector switch is actuated in response to rotationof the motor to control the desired intermittent operation. Theapparatus of this invention can be constructed of relatively simplecomponents which are readily available commercially.

In the accompanying drawing,

FIG. 1 is a schematic representation of a polymerization reactor havingthe valve control apparatus of this invention incorporated therein.

FIG. 2 is a schematic circuit drawing of an embodiment of the controlapparatus of this invention.

Referring now to the drawing in detail and to FIG. 1 in particular,there is shown a polymerization reactor which is provided with a jacket11 through which a coolant can be circulated. Such a coolant isintroduced through a conduit 12 and withdrawn through a conduit 13.Monomer, solvent and catalyst are introduced into reactor 10 throughrespective conduits 14, 15 and 16. The product is withdrawn through aconduit 17. Catalyst, which preferably is supplied in the form of aslurry, is introduced through conduit 16 at a rate which is controlledby the frequency at which a rotary valve l8'is actuated.

The polymerization system of FIG. 1 can be controlled by means of a heatbalance computer 19 of the type described in U.S. Pat. No. 3,078,265.This computer receives signals representing variables in the reactionsystem and provides an output signal which is representative of thepolymerization rate. This output signal is applied to the input of acontroller 20. Controller 20 also receives a set point signal 21 whichis representative of the desired rate of polymer production. In responseto a comparison of two input signals, controller 20 establishes anoutput signal which is applied to valve control means 22 to operatevalve 18 to control the rate of catalyst addition.

Control means 22 is illustrated in FIG. 2. Controller 20 provides anoutput electrical signal, the amplitude of which is representative ofthe desired rate of catalyst flow through conduit 16. This signal isapplied to input terminals 23aand 23b'of FIG. 2. Terminals 23a and 23bare connected to the input of a pulse generator. 24 which establishesoutput pulses at a frequency which is proportional to the amplitude ofthe input signal. The output signal from pulse generator 24 actuates arelay 25 which serves to move a switch 26 into engagement with aterminal 27 when the relay is energized. Switch 26 is thus closed at afrequency which is proportional to the amplitude of the output signalfrom controller 20. A linear integrating totalizer of the type describedin Data Sheet 197-101 of Moore Industries, Inc. of Van Nuys, Californiacan be employed as the pulse generator, for example. Such a totalizeractually includes switch 26 as an integral part thereof. The pulsegenerator can be selected to provide approximately 330 pulses per hour,for example, when a maximum amplitude output signal is received fromcontroller 20.

The apparatus of FIG. 2 includes two additional relays 28 and 29, thelatter being a time delay relay on closing which can be of the order of2 seconds, for example. When relay 28 is energized, switches 30 and 32engage respective terminals 31 and 33. When relay 29 is energized, aswitch 34 engages terminal 35 after the delay. At the same time, aswitch 36 is moved out of engagement with a terminal 37. Relays 28 and29 are energized from a voltage source 40, which can be either a director alternating source, depending on the type of relays employed. Thefirst terminal of source 40 is connected to a switch 41 whichselectively engages either a terminal 42 or a terminal 43. Switch 41 iscontrolled by a cam 44 which is mounted on the drive shaft of a motor45. A voltage source 46 is connected to motor 45 by parallel switches 34and 30. The drive shaft of motor 45 is connected to valve 18 to actuatethe valve in the manner to be described. Terminal 42 is connected toswitch 26 and to terminal 33. Terminal 43 is connected to switch 36 andto one terminal of relay 29. The second terminal of relay 29 isconnected to the second terminal of voltage source 40. Terminal 27 isconnected to one terminal of relay 28, the second terminal of which isconnected to the second terminal of voltage source 40. Switch 32 isconnected in parallel with switch 26.

Valve 18 is illustrated schematically in FIG. 2. This valve includes arotatable plug 18a which is provided with a central chamber 18b. A ball18c is disposed in chamber 18b so as to be free to move longitudinallythrough chamber 18b, thereby forming a rotary check valve. When the plugis in the position illustrated, catalyst slurry fills valve chamber 18babove ball 18c. When the plug is rotated this slurry is trapped in theplug. When the plug is rotated an additional 90, the trapped slurry isdisplaced from the valve and flows into reactor 10.

In order to describe the operation of the apparatus of FIG. 2, it willbe assumed that plug initially is in a position 90 from that illustratedand switch 41 is in engagement with terminal 42. When an output pulse isreceived by relay 25, switch 26 is closed to energize relay 28. Thiscloses switches 30 and 32, the latter serving to latch relay 28 in theenergized position. Closure of switch 30 results in motor 45 beingenergized to rotate plug 18a approximately 90 to the positionillustrated. After this 90 rotation, cam 44 moves switch 41 out ofengagement with terminal 42 and into engagement with terminal 43,thereby deenergizing relay 28 to terminate rotation of motor 45. Switch41 then applies current to time delay relay 29, which results in therelay being actuated after the short delay. This delay permits thecatalyst slurry previously trapped in chamber 18b to be emptied and anew mass of slurry to fill the chamber. When relay 29 is actuated,switch 34 is closed to once again energize motor 45. Rotation of plug18a continues for another 90, at which time cam 44 moves switch 41 outof engagement with terminal 43 and into engagement with terminal 42.Motor 45 then remains stationary until another pulse is received byrelay 25 to initiate another cycle of operation. Cam 44.is designed sothat the foregoing operation is repeated when the cam is rotated thefollowing 180. An indicating lamp 50 is connected between terminal 37and the second terminal of'voltage source 40. Each time relay 29 isenergized, lamp 50 is extinguished to provide a visual indication thatthe circuit is operating. As an alternative, lamp 50 can be actuated bythe closing of a switch corresponding to 36 in response to relay 29being energized. A terminal 51 is connected to relay 28 so that theapplication of a potential to terminal 51 results in relay 28 beingenergized. This permits the apparatus to be operated manually byapplying a potential to terminal 51.

7 While this invention has been described in conjunction with .apresently preferred embodiment, it obviously is not limited firstswitching means actuated by rotation of said motor to move periodicallybetween first and second positions;

second switching means;

means responsive to the input signal to close said second switchingmeans periodically at a rate representative of said input signal;

first control means including said first and second switching means toconnect said source of current to said motor when said first switchingmeans is in said first position and said second switching means isclosed, said first control means including latching means actuated bysaid second switching means to retain said source of current connectedto said motor until said first switching means is moved to said secondposition; and

second control means including said first switching means to connectsaid source of current to said motor when said first switching means isin said second position.

2. The apparatus of claim 1 wherein said second control means includestime delay means to delay the connection of said source of current tosaid motor after said first switching means is moved to said secondposition.

3. The apparatus of claim 1 wherein said input signal is an to closesaid second switching means comprises a pulse generator-adapted toprovide a series of output pulses at a frequency proportional to theamplitude of said input signal.

4. The apparatus of claim 1 wherein said first switching means isactuated by a cam which is rotated by said motor, said cam being of suchconfiguration that said first switch is moved each time said cam isrotated approximately 90.

. electrical signal of variable amplitude, and wherein said means 5. Theapparatus of claim 1, wherein said control element comprises a plugvalve, said plug valve having a rotatable plug with a chamber therein,and a ball movable through said chamber to form a double check valve.

6. Apparatus for actuating an intermittent motion control element inresponse to an input signal comprising:

a motor connected to said control element;

a first source of current to energize said motor;

first, second, third and fourth switches;

means responsive to said input signal to close said first switchperiodically at a rate representative of said input signal;

a fifth switch actuated by rotation of said motor to engage first andsecond contacts periodically;

a first relay to close said secondand third switches when energized; k

a time delay relay to close said fourth switch a predetermined timeafter being energized;

a second source of current;

first circuit means to connect said first source of current to saidmotor when either of said second and fourth switches is closed;

second circuit means to connect said first relay to said second sourceof current when said fifth switch engages said first contact and eitherof said first and third switches is closed; and

third circuit means to connect said time delay relay to said secondsource of current when said fifth switch engages said second contact.

1. Apparatus for actuating an intermittent motion control element inresponse to an input signal comprising: a motor connected to saidcontrol element; a source of current to energize said motor; firstswitching means actuated by rotation of said motor to move periodicallybetween first and second positions; second switching means; meansresponsive to the input signal to close said second switching meansperiodically at a rate representative of said input signal; firstcontrol means including said first and second switching means to connectsaid source of current to said motor when said first switching means isin said first position and said second switching means is closed, saidfirst control means including latching means actuated by said secondswitching means to retain said source of current connected to said motoruntil said first switching means is moved to said second position; andsecond control means including said first switching means to connectsaid source of current to said motor when said first switching means isin said second position.
 2. The apparatus of claim 1 wherein said secondcontrol means includes time delay means to delay the connection of saidsource of current to said motor after said first switching means ismoved to said second position.
 3. The apparatus of claim 1 wherein saidinput signal is an electrical signal of variable amplitude, and whereinsaid means to close said second switching means comprises a pulsegenerator adapted to provide a series of output pulses at a frequencyproportional to the amplitude of said input signal.
 4. The apparatus ofclaim 1 wherein said first switching means is actuated by a cam which isrotated by said motor, said cam being of such configuration that saidfirst switch is moved each time said cam is rotated approximately 90* .5. The apparatus of claim 1, wherein said control element comprises aplug valve, said plug valve having a rotatable plug with a chambertherein, and a ball movable through said chamber to form a double checkvalve.
 6. Apparatus for actuating an intermittent motion control elementin response to an input signal comprising: a motor connected to saidcontrol element; a first source of current to energize said motor;first, second, third and fourth switches; means responsive to said inputsignal to close said first switch periodically at a rate representativeof said input signal; a fifth switcH actuated by rotation of said motorto engage first and second contacts periodically; a first relay to closesaid second and third switches when energized; a time delay relay toclose said fourth switch a predetermined time after being energized; asecond source of current; first circuit means to connect said firstsource of current to said motor when either of said second and fourthswitches is closed; second circuit means to connect said first relay tosaid second source of current when said fifth switch engages said firstcontact and either of said first and third switches is closed; and thirdcircuit means to connect said time delay relay to said second source ofcurrent when said fifth switch engages said second contact.